I prepared a 'Chicago thin crust' pizza by flattening out a 12" dough into a 14" deep dish pan.

460 degrees for 25 minutes, then cover with foil and bake an additional 10 minutes to crisp the crust.

Sorry, no photos this time.

First impression: Since I've never worked with spelt before, I'd say it was a pretty successful test. The crust set up fine and I'm sure it will be plenty sturdy for deep dish use. Although the spelt did add a nice nutty flavor to the crust, it also made the texture a little gritty.Next time, I'll try 25% and see if that reduces the grittiness. Perhaps a bit more water to the dough as well.

I think spelt would work really well for deep dish since there is little gluten development to be done on these crusts. Spelt is low in gluten and your instinct to lower to 25% is a good one. You may not need to adjust the hydration at that percentage. But you have much more experience with DD so go with what you feel is the right direction.